The present invention generally relates to computer peripheral devices coupled to a host computer, and more particularly to an image data processing terminal equipment, such as a printer, an image scanner, a modem (modulator and demodulator) or the like.
There are previously known, as peripheral devices of a host computer, a printer, an image scanner, or a modem. The printer is supplied with information which is processed and output by the host computer, and prints out characters and/or graphics based on the supplied information. The image scanner optically reads a document and outputs a corresponding electrical signal to the host computer. The facsimile machine is supplied with information related to an original which is to be sent to a destination terminal, and outputs the same to a communication line.
Some peripheral devices have a large-capacity storage device and/or a plurality of different data processing functions. For example, a page printer such as a liquid printer or a laser beam printer is presently widely used. Such a page printer is equipped with a large-capacity RAM (random access memory) since an image amounting to one page must be formed in a storage area. A page printer which has a storage capacity enabling images equal to a plural number of pages to be stored simultaneously is also available. Such a page printer can operate at higher speeds and realize a duplex print. Some available printers can be connected to not only an extended RAM but also an extended hard disk drive unit, such as a magnetic disk unit. Conventional hard disk units have the ability to store fonts and initial commands which are used when the power supply to the printers is started.
It will be noted that the host computer cannot use the storage area provided by the extended RAM or extended hard disk unit. The storage capacity available in the printer tends to be increased. However, the storage area in the printer is used by the printer only when a print request command, which is, in general, temporarily generated, occurs. In addition, it is impossible for the host computer to use the storage area provided in the printer. Thus, the storage area in the printer is not used economically. Of course, extended RAMs or hard disk units themselves are expensive.
Further, conventional systems having a host computer and a printer are not designed to read out predetermined data from the storage area in the printer after the predetermined data is written therein. For example, it is impossible to read out down load font (font data), forms overlay data (print format data) and micro commands from the printer after the data are written therein.
Page printers are required to perform an image processing at high speeds and thus have high performance hardware and software which is often equivalent or superior to that of a personal computer, which serves as the host computer. However, the high-performace hardware and software work only when the printer is performing the image processing, and is thus idling when the printer is not carrying out the image processing.
As has been described previously, image scanners function as the peripheral devices of the host computer. Some image scanners have hardware which implements an image processing such as a data compression process. However, it is possible for peripheral devices other than the image scanner to utilize such an image processing implemented by the image scanner.
Some facsimile machines or modems have a data compression/decompression procedure and/or a data scrambling/descrambling procedure. However, it is impossible for other peripheral devices to use such procedures.